Standard Interpretations - Table of Contents
• Standard Number: 1910.1000; 1910.1200; 1910.1200(e); 1910.1200(f); 1910.1200(g); 1910.1200(h)


This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any situation not delineated within the original correspondence.


May 19, 2009

Gerald S. Zavorsky, Ph.D.
Department of Obstetrics, Gynecology and Women's Health
School of Medicine/Saint Louis University
6420 Clayton Road, Suite 290
St. Louis, MO 63117

Dear Dr. Zavorsky:

Thank you for your February 19, 2009, letter, to the Occupational Safety and Health Administration (OSHA). Your letter has been referred to the Directorate of Enforcement Programs for an answer to your question regarding the permissible exposure limit (PEL) for nitric oxide (NO). This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any question not detailed within your original correspondence.

Question: Does the OSHA PEL for nitric oxide, which is 25 parts per million (ppm) as an 8-hour time-weighted average (TWA), apply to pregnant women? If not, what is the OSHA PEL for pregnant women exposed to nitric oxide?

Reply: OSHA's Air Contaminants standard (29 CFR 1910.1000) provides limits for employee exposures. In Table Z-1 of 1910.1000, limits for air contaminants are provided for many substances, including nitric oxide. OSHA's permissible exposure limit of 25 ppm for occupational exposure to nitric oxide measured as an 8-hour TWA is applicable to all employee exposures to nitric oxide, including employees who may be pregnant. Please be mindful that, in addition to the requirement to limit occupational exposures to a level below the OSHA PEL, employers may have other responsibilities for ensuring